SACRAMENTO, Calif., Dec. 6, 2017 — A fluorescence-based, slide-free optical imaging system, known as microscopy with UV surface excitation (MUSE), uses UV light at wavelengths below the 300-nm range to penetrate the surface of tissue samples by only a few microns — about the same thickness of tissue slices on traditional microscope slides. The MUSE technology is a nondestructive technique that, within minutes, can provide high-resolution diagnostic images resembling those obtained from conventional haematoxylin and eosin (H & E) histology.

MUSE technology captures breast tissue with nerves coursing over and through a layer of intact fat cells. Courtesy of Richard Levenson, UC Davis.Researchers at the University of California, Davis, Health System demonstrated that 280-nm UV excitation, generated by widely available LED sources, could penetrate tissue to about the thickness of a typical tissue section. The technology was tested on an array of normal and neoplastic tissues and, according to researchers, generated images with high spatial resolution and contrast, showing not only the overall tissue architecture, but also nuclear chromatin texture and mitotic figures. The samples were stained with inexpensive fluorescent dyes within seconds. Resulting images could be color-mapped in real time to replicate standard H&E staining.

Samples that were stained with eosin or other standard dyes to highlight features such as nuclei, cytoplasm and extracellular components produced signals from excitation light in the sub-300-nm spectral range that were bright enough to be detected by conventional color cameras using subsecond exposure times, making it possible to quickly gather high-resolution images without destroying tissue. Despite being excited in the relatively deep UV, the stains emitted photons in the visible range, and the visible-band signals could be captured using conventional glass-based microscope optics and either grayscale or color cameras.

While MUSE images can resemble those from standard histology slides and bright-field microscopes, they can also provide surface and color contrast features not usually present in H&E preparations. Conventional bright-field microscopy requires prior preparation of micrometer-thick tissue sections mounted on glass slides — a process that can require hours or days, delaying access to critical information.

MUSE has the ability to gather high-resolution images without consuming the tissue.

MUSE image of kidney artery. Courtesy of Richard Levenson, UC Davis.“It has become increasingly important to submit a relevant portion of often tiny tissue samples for DNA and other molecular functional tests,” Levenson said. “Making sure that the submitted material actually contains tumor in sufficient quantity is not always easy, and sometimes just preparing conventional microscope slices can consume most or even all of a small specimen. MUSE is important because it quickly provides images from fresh tissue without exhausting the sample.”

MUSE has the potential to generate images of diagnostic quality and could improve the speed and efficiency of patient care in both state-of-the-art and low-resource settings and provide opportunities for rapid histology in research.